Technical battery light and charging voltage?

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Technical battery light and charging voltage?

dac69er

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fix one thing and something else breaks :mad:

anyway, on my way home tonight i noticed that as my rpm dropped to <2000rpm-ish, my battery light came on dimly. during normal driving its perfectly fine.

i check the charging voltage and it was @ about 14v on idle. if i rev it up it doesnt really alter much.
battery voltage was @ 13v, but i had only just stopped driving.

battery is brand new about a month ago. same with the alternator belt.
car runs fine, putting more or less load on the electrical system doesnt make any difference to the brightness of the light. sometimes the light will go off for a bit and then flicker back on without doing anything to it.

i would assume alternator, but the charging voltage seems reasonable to me. any ideas?
 
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Check the connections are clean and sound on the alternator.

Had a go going that this morning. Thought it had cured it, but if I look really carefully I can see that it is just showing the battery light still.
It is very faint, but still on, only on idle, gets ever so slightly brighter if I put the lights on.
 
Alternator is dead. Get a replacement before it gives up completely.

Not necessarily (though i agree it's probably the most likely), however whilst charging voltages seem ok, it's worth doing the free things like cleaning up connections before shelling out on a replacement. If they were suspect at all (and i think it needs tested again when the light is on, with a full load on battery), then it'd defo be replacement time.

Mine did similar with an erratic battery light appearing at idle, going off then staying off, later came on and wouldn't go off, then randomly 3 days later did go off all with good charging voltage then my battery died a very early death and couldn't be revived (less than one year old) so suspect it was doing all sorts of funky things and had to replace both alt and bat in the end.
 
Had a go going that this morning. Thought it had cured it, but if I look really carefully I can see that it is just showing the battery light still.
It is very faint, but still on, only on idle, gets ever so slightly brighter if I put the lights on.

Before you spend a lot, change the regulator and brushes. Cheap and easy.
Don't know what alternator you have, but see ebay item 290969714086 for a typical Cinq part - under £12
smile.gif


Robert G8RPI.
 
Just removed the alternator. I had already been through all the ground connections this morning.

The alternator has already been reconditioned at some point as it has QH stickers on it.

Looking online, regulator and rectifier are about £35 or do I bite the bullet and just get a complete recon unit for £60!!!!
 
Often the brushes have worn the slip rings. Replacing slip rings is difficult and best left to the reconditioners. If you can easily remove the brush box, often part of the regulator, you can see the slip rings. If they are ok, then replace rectifier and regulator. If worn, replace the whole unit.

Personally I'd replace the whole thing, get a guarantee. Most should come with a 2-yr warranty.
 
on deeper investigation it appears the rectifier has come apart where it should be riveted together. that may have caused failure due to vibration perhaps!?

slip rings look ok to me. i have managed to find the regulator/brushes and the rectifier for under £30 so have gone with that.
i would much rather do the job myself if i can. i only ever get specialist machine work farmed out as i dont have the gear to do that myself :)

will let you all know how i get on once i have all the new bits and it is refitted.
thanks for your help.
 
2 new bearings and new electrical bits and it's running sweet again. Changing the rectifier is a bit of a pain job, but got there in the end. The brushes and regulator were serviceable but replaced them anyway as I had the part.

No battery light and charging voltage is now 14.36v
 
To be honest the new parts were more than a replacement alternator off eBay. But who knows how long a second hand unit would last!?
 
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